Buggy Filter

[Mohammad]

I was working with TW5.18-pre and wrote a macro as below inside a new tiddler

\defime buggy(filter)

<$list filter='[$filter$allbefore:include{!!current-item}]' variable="myTid">

<$transclude tiddler=<<myTid>> mode="block"/>

</$list>

\end

NOTE to my mistake, I used defime instead of define

Note that, here actually the macro is bypassed as it was incorrect and this is the filter and list widget which cause the problem.

I was in preview mode, I noted TW frozen! No response for a while and then throughout a lot of Javascript!

What is the problem? Is this a bug?

-Mohammad

[PMario]

On Wednesday, October 17, 2018 at 7:27:36 AM UTC+2, Mohammad wrote:

What is the problem?

As you found out your "defime" typo. .. So that's not a macro definition. It's just wikitext.

The list is executed with some missing parameters. eg: $filter$ because it's empty. .. So you basically transclude all tiddlers and show them with

<$transclude tiddler=<<myTid>> mode="block"/> 

It's just a long list that is transcluded.

Is this a bug?

No ... your typo.

-mario

[Mohammad]

Yes, the filter is empty so, why the .js tiddler are transcluded?

The first tiddler transcluded is $:/library/sjcl.js

Why allbefore empty is some .js tiddlers?

I expect an empty result.

Mohammad

[Jeremy Ruston]

Hi Mohammad

Just to clarify what’s going on, the filter expression "[$filter$allbefore:include{!!current-item}]” is interpreted as an invocation of the filter operator “$filter$allbefore” (the $filter$ is treated literally since we’re not inside a macro) with the suffix “include” and the operand transcluded from the “current-item” field of the current tiddler. Because there usually isn’t such a field present, the operand will be read as a blank string. Meanwhile, because the filter operator doesn’t exist, the system falls back to using the “field” operator, making the whole expression equivalent to “[field:include[]]” which will look for tiddlers with a blank field “include”. Perhaps unexpectedly, the “field” operator treats tiddlers with a missing field as if the field was blank.

By the way, the technique I used to explore this filter was to run the following in the developer console of tw5.com:

$tw.wiki.parseFilter("[$filter$allbefore:include{!!current-item}]")

The result is a simple JSON representation of the syntax tree, which can help you to understand how the system is seeing the filter.

Best wishes

Jeremy.

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[Mohammad]

Many thanks Jeremy for this complete explanation!

Cheers

Mohammad